The
nature of the public network has changed. Demand for Internet Protocol (IP) data
is growing at a compound annual rate of between 100% and 800%1, while voice demand
remains stable. What was once a predominantly circuit switched network handling
mainly circuit switched voice traffic has become a circuit-switched network handling
mainly IP data. Because the nature of the traffic is not well matched to the underlying
technology, this network is proving very costly to scale. User spending has not
increased proportionally to the rate of bandwidth increase, and carrier revenue
growth is stuck at the lower end of 10% to 20% per year. The result is that carriers
are building themselves out of business.Over
the last 10 years, as data traffic has grown both in importance and volume, technologies
such as frame relay, ATM, and Point-to-Point Protocol (PPP) have been developed
to force fit data onto the circuit network. While these protocols provided virtual
connections-a useful approach for many services-they have proven too inefficient,
costly and complex to scale to the levels necessary to satisfy the insatiable
demand for data services.

More recently, Gigabit Ethernet (GigE) has been adopted
by many network service providers as a way to network user data without the burden
of SONET/SDH and ATM. GigE has shortcomings when applied in carrier networks were
recognized and for these problems, a technology called Resilient Packet Ring Technology
were developed. RPR retains the best attributes
of SONET/SDH, ATM, and Gigabit Ethernet. RPR is optimized for differentiated IP
and other packet data services, while providing uncompromised quality for circuit
voice and private line services. It works in point-to-point, linear, ring, or
mesh networks, providing ring survivability in less than 50 milliseconds. RPR
dynamically and statistically multiplexes all services into the entire available
bandwidth in both directions on the ring while preserving bandwidth and service
quality guarantees on a per-customer, per-service basis. And it does all this
at a fraction of the cost of legacy SONET/SDH and ATM solutions.